Problem: You have found the following ages (in years) of 4 tigers. Those tigers were randomly selected from the 47 tigers at your local zoo: $ 14,\enspace 13,\enspace 16,\enspace 3$ Based on your sample, what is the average age of the tigers? What is the standard deviation? You may round your answers to the nearest tenth.
Explanation: Because we only have data for a small sample of the 47 tigers, we are only able to estimate the population mean and standard deviation by finding the sample mean $({\overline{x}})$ and sample standard deviation $({s})$ To find the sample mean , add up the values of all $4$ samples and divide by $4$ $ {\overline{x}} = \dfrac{\sum\limits_{i=1}^{{n}} x_i}{{n}} = \dfrac{\sum\limits_{i=1}^{{4}} x_i}{{4}} $ $ {\overline{x}} = \dfrac{14 + 13 + 16 + 3}{{4}} = {11.5\text{ years old}} $ Find the squared deviations from the mean for each sample. Since we don't know the population mean, estimate the mean by using the sample mean we just calculated {6.25} + {2.25} + {20.25} + {72.25}} {{4 - 1}} $ {s^2} = \dfrac{{101}}{{3}} = {33.67\text{ years}^2} $ As you might guess from the notation, the sample standard deviation $({s})$ is found by taking the square root of the sample variance $({s^2})$ ${s} = \sqrt{{s^2}}$ $ {s} = \sqrt{{33.67\text{ years}^2}} = {5.8\text{ years}} $ We can estimate that the average tiger at the zoo is 11.5 years old. There is also a standard deviation of 5.8 years.